#include <fstream>

std::ifstream fin("./flip.in");
std::ofstream fout("./flip.out");

int matrice[17][17];

int main(){

    int n, m;
    fin >> n >> m;
    for(int i = 1; i <= n; ++i){
        for(int j = 1; j <= m; ++j){
            fin >> matrice[i][j];
        }
    }

    int suma = 0;
    for(int i = 1; i <= n; ++i){
        suma = 0;
        for(int j = 1; j <= m; ++j){
            suma += matrice[i][j];
        }
        if(suma < 0){
            for(int j = 1; j <= m; ++j){
                matrice[i][j] = -1 * matrice[i][j];
            }
        }
    }
    for(int j = 1; j <= m; ++j){
        suma = 0;
        for(int i = 1; i <= n; ++i){
            suma += matrice[i][j];
        }
        if(suma < 0){
            for(int i = 1; i <= n; ++i){
                matrice[i][j] = -1 * matrice[i][j];
            }
        }
    }
    suma = 0;
    for(int i = 1; i <= n; ++i){
        for(int j = 1; j <= m; ++j){
            suma += matrice[i][j];
        }
    }
    fout << suma;
    fin.close();
    fout.close();
    return 0;
}